Image forming apparatus having start and stop keys integrally connected in the same matrix circuit

ABSTRACT

An image forming apparatus includes an image forming mechanism for forming an image and a matrix circuit having connected thereto a plurality of keys including an initiating key for instructing the start of image formation and a stop key for interrupting image formation. The image forming apparatus further includes a controller for controlling image formation by the image forming mechanism in accordance with a control sequence and a memory containing a program for sensing key input of the matrix circuit. Prior to the start of image formation, the controller executes the program for sensing key input of the matrix circuit and executes the control sequence in response to the sensing input of the initiating key. During image formation, the controller executes the program for sensing key input of the matrix circuit such that sensing whether the stop key has been input is executed without sensing whether the initiating key has been input.

This application is a continuation of application Ser. No. 07/666,737, filed Mar. 8, 1991, now abandoned which is a division of application Ser. No. 07/405,487, filed Sep. 11, 1989, now U.S. Pat. No. 5,089,074, which was a continuation of application Ser. No. 07/008,119, filed Jan. 23, 1987, now abandoned, which was a continuation of application Ser. No. 06/675,650, filed Nov. 28, 1984, now abandoned, which was a continuation of application Ser. No. 06/288,211, filed Jul. 29, 1981, now abandoned, which was a division of application Ser. No. 05/882,614, filed Mar. 1, 1978, now U.S. Pat. No. 4,312,587. This application is related to application Ser. No. 07/456,578, filed Dec. 29, 1989, pending, which was a continuation of application Ser. No. 07/155,729, filed Feb. 16, 1988, now abandoned, which was a division of application Ser. No. 06/659,784, filed Oct. 11, 1984, now U.S. Pat. No. 4,763,164, issued Aug. 9, 1988, which was a division of application Ser. No. 06/288,211, filed Jul. 29, 1981, now abandoned, which was a division of said Ser. No. 06/882,614, now U.S. Pat. No. 4,312,587.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus adapted for use for example in a copier or a printer.

2. Description of the Prior Art

The process sequence control or timing control conventionally employed for example in copiers for controlling the process effecting means (equipment required for performing the steps of charging, imagewise exposure, development, transfer, fixing etc.) has been achieved by combinations of relay circuits or so-called hard wire logic circuits.

Such relay circuits or logic circuits, being designed and structured for a particular performance, require cumbersome redesigning and rewiring if there is any change in required performance. Also such circuits, if required to control several devices or to perform a complex control, result in extremely complicated structure and wirings, thus deteriorating the reliability and rendering the maintenance and inspection difficult.

Though there is also known a process sequence control system in which the sequence functions are pre-programmed, the drawback in complexity of circuit composition has not been solved.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image forming apparatus of a reduced dimension, which is capable of performing plural functions thereby avoiding the above-mentioned drawbacks.

Another object of the present invention is to provide an improved image forming apparatus capable of performing process sequence control according to a stored program for controlling the functions of equipment in response to the instructions and detections.

Another object of the present invention is to provide an improved image forming apparatus provided with various instructing and displaying devices for operator.

Another object of the present invention is to provide an image forming apparatus of a transfer process with an improved timing control for exposure and transfer sheet feeding.

Another object of the present invention is to provide an improvement in a copying apparatus for copying thin and thick originals with an elevated efficiency.

Another object of the present invention is to provide an improvement in a copying apparatus provided with a plurality of cassettes accommodating recording web.

Another object of the present invention is to provide an image forming apparatus with a control system utilizing enlarged computer performance.

Another object of the present invention is to provide a copying apparatus provided with a moving optical system for exposure achieving a highly stable function with an elevated precision.

Another object of the present invention is to provide a copying apparatus provided with a transfer sheet feeding means achieving a precise and stable function.

Another object of the present invention is to provide a small table-top copier of multiple functions.

The above-mentioned and other objects will be achieved by the embodiments to be described in the following.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of an example of a copier wherein the present invention is applicable;

FIG. 2 is a cross sectional view of a paper feed section thereof wherein a manually inserted cassette is utilized;

FIG. 3 is a cross sectional view of an optical system and an illuminating section of the present invention;

FIG. 4 is a perspective view showing an accuride utilized as a linear guide device;

FIG. 5 is a perspective view of a drive-guide section of the optical system;

FIGS. 6 and 7 are cross sectional views of the illuminating section;

FIG. 8 is a schematic drawing of a conventional linear guide device;

FIG. 9 is a cross sectional view of the paper feed section;

FIG. 10 is a perspective view thereof;

FIG. 11 is a perspective view of a clutch mechanism for controlling a paper feed device;

FIG. 12 is a perspective view thereof;

FIG. 13 is a cross sectional view of a conventional paper feed control clutch;

FIG. 14 is a perspective view of a loop forming guide plate;

FIG. 15 is an elevation view of a copy control section;

FIGS. 16 (which comprises FIGS. 16A, 16B and 16C), 17 (which comprises FIGS. 17A, 17B and 17C), 18 (which comprises FIGS. 18A and 18B) and 19 (which comprises FIGS. 19A and 19B) are flow charts of sequence control;

FIG. 20 (which comprises FIGS. 20A and 20B) is a flow chart of key entry;

FIG. 21 (which comprises FIGS. 21A and 21B) is a time chart in book mode;

FIGS. 22 and 23 are time charts in sheet mode;

FIG. 24 is a circuit diagram for achieving the time charts shown in FIGS. 22 and 23;

FIG. 25 is a control block diagram of the present invention wherein a computer is employed;

FIGS. 26(A) (which comprises FIGS. 26A' and 26A"), (B), (C), (D) and (E) are a circuit diagram, a name list, a pulse wave chart, a drawing of a cassette change cam, and a logic circuit, respectively, corresponding to FIG. 25;

FIG. 27 is a diagram of an embodiment of the matrix circuit in FIG. 26;

FIG. 28 is an internal circuit diagram of CPU in FIG. 26;

FIG. 29 is an illustration of register addresses of the RAM in FIG. 28;

FIG. 30 (including FIGS. 30A and 30B) are a partial flow chart of the control by CPU; and

FIGS. 311-1A through 31-1F, 31-2A through 312-2C, 313-3a through 31-3c, 314-4A through 31-4C, 315-5, 316-6A through 31-6C, and 31-7A through 317-7C) are flow charts of the control by CPU.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Machine)

Referring to FIG. 1, an original 1 is placed on a glass plate of an original table 2 constituting an original supporting face on the upper surface of the machine casing, and is subjected to a slit exposure by means of an optical system consisting of an illuminating lamp 3, a first mirror 4 displacing integrally therewith, a second mirror 5 displacing in a same direction as that of said first mirror 4 with a velocity half of that of said first mirror 4, a switching mirror 6, a lens 7 and a fixed mirror 8, thereby to form an image of said original onto a drum 9.

The surface of said drum 9, which is an endless photosensitive member comprising an insulating surface layer, a photoconductive layer and a conductive base, is electrostatically charged with a charger 10, and, upon reaching the exposure section 11, is exposed to the image of the original, combined with simultaneous charge elimination by means of a charge eliminator 12.

The photosensitive drum surface is successively subjected to a flush exposure by a flush exposure lamp 13 to form an electrostatic latent image on said surface, and is introduced into a developing station 14.

The development is conducted by wet process utilizing a developing roller 15. Successively the excessive developing liquid is squeezed by a post-charger 16.

Then the image formed on said drum 9 is transferred, by means of a transfer charger 17, onto a copy sheet 20 supplied from a feed section 18 or 19.

The copy sheet, after the transfer, is separated from the drum 9 in the separating section 21, then is fixed in a fixing section 22 and ejected by means of an ejecting roller 23 onto a tray 24. On the other hand the photosensitive drum surface is cleaned by a blade 25 maintained in pressure contact with said surface to remove remaining toner on said drum, and is thus prepared for the succeeding cycle. In case of copying a bound original, the switching mirror 6 is placed in a position represented by double-dot chain lines.

An automatic feed device 26 for sheet originals can be utilized when the switching mirror 6 is placed in the full-line position and the moving mirrors 4, 5 are placed at the right end (full-line positions). In this case the original passing through the exposure section 30 is illuminated by the lamp 3, and the image of said original is formed, by means of said switching mirror 6, lens 7 and fixed mirror 8, onto the drum 9. Said lamp 3 is same as that used for the bound original. The sheet originals 28 are stacked on an original table 27 of the automatic feed device 26, and an uppermost sheet is separated by means of a separating roller 29 and conveyed, by means of a series of feed rollers 31, 32, 33 and 34, through the exposure section 30 to the original tray 35.

Automatic continuous feeding of sheet originals can be achieved by said automatic feed device 26. Also by making the transfer speed of said feed rollers 31-34 somewhat faster than that of said separating system 29, it becomes possible to provide a gap between the succeeding sheet originals whereby the detection of the leading or trailing end of each sheet original is facilitated.

FIG. 1 shows a state wherein either a main cassette 73 or a sub-cassette 74 is usable, in connection therewith an upper or a lower feed roller 53 being actuated by means of a switching button.

FIG. 2 shows a state wherein a manually inserted cassette 75 is used. A cassette receiver 80 is articulated to an axis 76 fixed on the main body.

The manually inserted cassette 75 is slidably mounted on a cassette receiver 77, of which an extremity is fixed to a shaft 79 articulated on the main body. The shaft 79 is rendered swingable by means of a motor and the position thereof is selectable by means of a button.

Also as shown in FIG. 2, there are provided paper detecting elements (a lamp and a light-receiving element 103) in a position in the copy sheet path corresponding to the distance 1 between the exposure section and the transfer section. Upon detection of the trailing end of a copy sheet the optical system is reversed by a control to be explained later.

Now referring to FIGS. 3 to 7 there will be given an explanation on the guiding of the optical system and on the illuminating section.

The first mirror 4 is fixed on a supporting member 36 which is coupled with an inner member 37 of a linear guide known under a trade name "Accuride". The Accuride is provided, as shown in FIG. 4, with a structure of a plurality of rollers 40 retained by a retainer 39 within two linear spaces each composed of grooves respectively formed on an inner member 37 and an outer member 38, whereby said inner member 37 is guided linearly with respect to said outer member 38. Said spaces confining said rollers 40 are dimensioned slightly smaller than the outer diameter thereof to give a predetermined pressure thereto whereby a relative movement without play being realized between said inner and outer members. As shown in FIG. 5, the outer member 38 covers the stroke of said first mirror 4 and is mounted to the machine frame (not shown) by means of mounting members 41. The inner member 37, being of a length substantially equal to that of mounting portion of the supporting member 36 for said first mirror, is guided over the full length of said outer member, riding switchingly on many rollers 40. On the other end of said supporting member 36 there is provided a roller 42 supported by a rail 43 fixed to the main body.

The second mirror 5 is fixed to a supporting member 44 which is in turn fixed to an inner member 37 of a downwardly fixed Accuride. A conventional linear guide system is schematically shown in FIG. 8, wherein mirror supporting members 36, 44 are linearly guided along a rod-shaped rail 45 supported on both ends thereof. Such system is unable to guide the mirrors stably and with high precision because (1) the rail 45, being only supported by the both ends thereof, is of a limited rigidity, (2) the span (l) of supporting portion particularly of the supporting member for the first mirror has to be limited in order to avoid mutual interference of supporting portions of said supporting members, and (3) a certain play is inevitable between the rod and the thrust bearing fitted thereon. In contrast thereto, the mechanism according to the present invention enables a stable reciprocating movement with an extremely high precision because (1) the Accuride can be fixed, at any portion thereof, to the main body, (2) the Accuride itself has a large dimension with an accordingly enlarged cross section, (3) the supporting span (l) can be made satisfactorily large as there is no mutual interference between the supporting portion of the Accuride and the supporting portions of supporting members for the first and second mirrors, and (4) there exists no play between the inner and outer members as explained before.

In FIG. 3 the full-lined positions are home positions from which the first and second mirrors 4, 5 are displaced to the right to perform scanning of the original, and, upon completion thereof, are returned to said home positions by means of a spring 45. In case a button for automatic feed device for sheet originals is actuated, the mirror 5 is displaced by means of a clutch motor to the chain-lined position at right and locked there as to be explained later. In this case the lamp 3 is displaced to a position allowing illumination of sheet originals. The details of related portion are shown in FIGS. 6 and 7.

FIG. 6 shows a state of scanning an original placed on the glass plate of original table 2. A supporting arm 46 fixed to the mirror supporting member 36 is provided with an axis 47, on which rotatably supported is an integral structure of an illuminating lamp 3, a reflector 48 and a supporting follower 49, wherein said follower 49 being provided at an end thereof with a roller 50 to enable the function thereof as a follower. FIG. 6 shows the details in the vicinity of the first mirror 4 during the copying of a bound original, while FIG. 7 shows the details in the vicinity of the illuminating section while the automatic feed device for sheet originals is in function. Upon displacement to the right-hand end, the first and second mirrors mutually approach due to the speed difference therebetween. The supporting member 44 for the second mirror is provided with a cam plate 51, which is traced by said roller 50 to direct the lamp 3 and the reflector 48 toward the exposure section 30 of a sheet original as shown in FIG. 7.

Now there will be given a detailed description on the paper feed section while referring to FIGS. 9, 10, 11 and 12. A paper feed roller 53 is fixed on an axis 54 thereof which is rotatably supported on an arm 55. Said arm 55 is provided with a fixed shaft 56 which is rotatably supported by the main frame, whereby said paper feed roller 53 is rendered rotatable around the shaft 56. The arm 55 is further provided with a spring 57 biasing said arm upwards. The axis 54 is provided with a follower roller following a cam 59 which is controlled by a single-rotation clutch adapted to making an intermediate stop during rotation, as explained in the following with reference to FIGS. 11 and 12. A cam shaft 60, passing through and supported by a frame 61, is provided with a pulley 63 which is driven by a motor through a belt 62. A spring clutch consisting of a drum portion 63₁ of said pulley 63, a clutch drum 64 fixed on said shaft 60, a clutch spring 65 and stop ring 66 is controlled by a solenoid 67. When the solenoid 67 is not energized, a lever 68 is located in a full-lined position in FIG. 11 to engage a projection 66₁ of said stop ring with said lever 68 thereby maintaining the clutch in disconnected position. Upon energizing of the solenoid 67 the lever 68 is displaced to a chain-lined position 68' to release the engagement with said projection 66₁ whereby the clutch is connected to cause rotation of the cam 59. However, upon rotation of ca. 180°, another projection 66₂ becomes engaged with the lever 68' to again disconnected the clutch, whereby the paper feed roller 53 is lowered by said cam 59 to a chain-lined position 53' shown in FIG. 9.

In said lowered position a friction pulley 69 (FIG. 10) provided on one end of the paper feed roller shaft 54 comes into friction contact with a constantly driven capstan 70 (FIGS. 9, 10) to drive said paper feed roller 53.

Deactivation of solenoid 67 disengages the projection 66₂ from the lever to connect again the clutch, which is again disconnected upon returning to the original full-lined position in FIG. 11 after a rotation of ca. 180°. The clutch spring 65 is engaged at one end thereof with the stop ring 66 and at the other end thereof with the clutch drum 64 to maintain relative positional relationship between the projections 66₁, 66₂ of the stop ring 66 and the cam 59 even after repeated clutch functions.

Such intermediate stop function of the cam is useful in increasing the design freedom, as the stopping can be freely selected by the period of solenoid activation.

FIG. 13 shows a conventional example of cam control mechanism for achieving such intermediate stop, wherein (66) is a stop ring, (66₁) and (66₂) are recesses for stopping said stop ring, and (b) and (c) are levers provided rotatable around a shaft (d) to engage with said recesses. A lever (a) with a pin (a') is rotated by a solenoid (67) around said shaft (d) to control said levers (b) and (c). Though a detailed explanation of the functions of such conventional system is omitted herein, the mechanism of the present invention is apparently simpler than such conventional system, and is therefore cheaper and more reliable. In contrast, the coventional system is inevitably of a lower reliability and of a higher cost due to the accumulated precisions (allowances) of component parts and to complex mutual movements of the component parts.

Now referring to FIG. 9, a paper sheet ejected from a cassette 73, 74 or 75 is advanced as indicated by double-dotted chain line P by the direction of ejection, rigidity and weight of paper, thus coming into contact with register rollers 52 which are in stopped state to form a loop P', and is further advanced upon start of rotation of said rollers 52. Such conventional paper feed mechanism often fails to form a desired loop P' but results in paper jamming between the cassette 75 and a guide plate 71 resulting from formation of an inverted loop P". This is found out due to insufficient air supply between the paper and the guide plate 71 when the paper sheet is to be displaced from the state P to P' whereby the paper remains being pressed in the position P.

In order to prevent such trouble, therefore, the guide plate 71 and the lower guide plate 72 are respectively provided with plural openings 71₁, 72₁ for air supply as shown in FIG. 14. Said openings may be provided on either one of said guide plate. Though in the embodiment illustrated in FIG. 14 there are provided oblong openings in spreading arrangements toward the downstream in order to avoid engagement with paper sheet, a similar effect can also be obtained by providing plural circular openings.

(Control)

Now there will be given an explanation on the process control according to the present invention. The present invention is featured in that a high-speed continuous copying is rendered possible by controlling the functions of original feeding and other process means by the position of a transfer sheet after the start of feeding thereof, regardless of the size of said transfer sheet; further in that the process timing can be maintained unchanged through a process control achieved by reading a memory storing programmed process timing for book mode and sheet mode even when a mode is instructed after the process is started with another mode; further in that a limited number of output lines is effectively utilized in program control by counting the signals from load control signal lines and controlling the functions of plural loads; and further in that a limited number of input signal lines is effectively used to reduce the power consumption by combining the input means of instructing copy number and detecting copy state with the output signal lines of program control.

(Operation input section)

FIG. 15 shows a control for controlling the copier of the present invention.

120 is a display section for indicating the paper size in the cassette, 121 are display elements for indicating a selected cassette, 122 is a switch for selecting a manually inserted cassette, 123 is a switch for selecting the upper cassette, 124 is a switch for selecting the lower cassette, wherein said switches being retaining switches, each of which, upon actuation, turns off other switches. 125 are display elements for indicating the preset copy number and the number of copies made, 126 are ten keys for presetting the copy number, 127 is a clear key for correcting the preset copy number, 128W, 128P, 128L and 128J are display elements for respectively indicating Waiting, Paper lacking, Liquid lacking and Jammed paper, 129 is a stop button for temporarily interrupting the copying, 130 is a start button for book copy, and 131 is a start button for automatic feeding of sheet originals.

(Computer control)

In the following there will be given an explanation of an embodiment for performing the sequence and other controls of the above-mentioned copier by means of a microcomputer.

Now referring to FIG. 25 illustrating a block diagram of a circuitry therefor, 201 is a computer chip element, 202 is a matrix circuit for supplying input signals to said element 201, 203 is a means for detecting the state of the copier, 204 is a gate circuit for output signals from the computer, 205 is a driver circuit for driving the function elements, 208 is an oscillator assisting said drive, 206 is a decoder for performing displays by the signals from the computer, and 207 is a display means.

Now referring to FIG. 26 showing the details of the circuits in FIG. 25, the microcomputer chip 201, composed of an element TMS1000 manufactured by Texas Instruments, is provided with four data input terminals K1, K2, K4 and K8, output terminals θ1-θ4 as the output 1 and output terminals RO-R12 as the output 2. The output 1 terminals are used for indicating the copy number on the display elements D1 and D2, and connected thereto through a segment decoder. The output 2 terminals are utilized for function control of load elements and scanning of input matrix circuit.

(Peripheral circuits)

The aforementioned gate circuit is provided with so-called decoder function, by combining the signals from said output 2 terminals to obtain further diversified output signals.

Three display lamps for Feed Missing Display and for two Jam Displays are controlled by a single output terminal R10, but there is provided a counter for counting the clock signals for display from said terminal R10 to drive different lamps.

The gate circuit supplies the output signals from the CPU to the input matrix circuit and the output interface circuit.

Said interface circuit amplifies the signals from said gate circuit to drive solenoids and lamps. The AD loads are driven through triacs of which trigger signals are obtained as AND outputs with the output from the oscillator.

In the matrix circuit, the output signals from the output 2 terminals and from the gate circuit are utilized for scanning input for the matrix circuit. These scanning lines cross with the input lines to the microprocessor to constitute a matrix, and there are provided switches at the crossing points thereof corresponding to the input points (FIG. 27).

Thus, supposing that the numbers of scanning lines and microprocessor input lines are x and y respectively, the maximum possible number of switches is xy.

Said switches are composed of keyboard switches in the control section, microswitches for control signals, and other signal generating switches in various detection circuits (for example for detecting paper, for detecting master clocks etc.). Thus the input to the microprocessor (CPU) is performed upon release of an output signal of level 1 to the scanning lines.

Now the functions of the above-described circuit will be briefly explained in the following. The key input signals from the control section (signals from numeral ten keys, clear key, start keys) and from the jam reset switch are taken into the CPU upon receipt of the output terminal R0-R2 and R9 thereof and of a signal (signal indicating before start) from terminal R4 inverted by a gate 265. Said scanning signals are clock signal shown in FIG. 26(C). The 2-digit number thus taken into the CPU is stored in a RAM, and is displayed on the display elements D1, D2 by driving said elements alternately through the switching elements 266, 267 by alternate outputs from the terminals R11 and R12 and by selecting the necessary segments of said elements by the simultaneous 4-bit output from the terminals θ-θ4. Upon completion of preparatory step such as key entry, the signal from the terminal R4 starts the main motor and performs the pre-exposure. Also said signal from R4 designates the input switches in the matrix (for register signal RS generation, clock pulse CP generation and transfer paper discharge signal CPOS generation), thus enabling input of sequence timing signals when the drum is rotated by the main motor. Also the copy paper input signal CPIS and the stop signal STOP are supplied to the CPU utilizing the exposure lamp drive signal R6 and blank lamp drive signal R7. Under the condition that the drum is rotated, the primary charger, AC discharger, whole surface (flush) exposure lamp, paper feed plunger and register clutch are driven by the output signals from R0-R2. However said input instructions are blocked by the inverted signal of the R4 output signal. An output signal OS1 of a sheet original first detector 106 is supplied to the CPU upon receipt of an inverted output by a gate 268 of the paper feed plunger drive signal from R1 and of the sheet clutch drive signal from R1. Also the input into the CPU of a detection OS2 from a second detector 107 is achieved upon receipt of an AND output from a gate 270 receiving the register clutch drive signal from R2 and the transfer paper input signal. In this manner the input and output terminals of a limited number of a CPU can be effectively utilized. Also overlapped inputs can be prevented even if set signals from different output terminals are simultaneously supplied to the input matrix.

The optical system displacing motor is actuated by an AND output from a gate 271 receiving the output signals from the terminals R9 and R5. This will be later explained in detail in connection with the optical system position check in sheet mode.

The input signals relating to cassettes are supplied to the CPU by the set signal from the output terminal R3. The cassette selection signal and the cassette position detection signal are inputted by a short pulse from R3, and in case the manual cassette is selected (auxiliary cassette selection button AUX is ON), if the auxiliary cassette position detecting switch ACS is not ON, the set signal from R3 is continued until the switch ACS becomes ON whereby the cassette motor is switched on. Said motor does not start upon receipt of the initial set pulse.

The optical system home position detection signal OHP2 in sheet mode is inputted by the set signal from the output terminal R9. Upon identification of ON state thereof, the output terminals R5 and R9 are not set, and the optical system displacing motor is therefore not started. On the other hand, upon identification of OFF state thereof, the terminals R5 and R9 release set signals to activate the optical system displacing motor and the forward clutch to displace the optical system in a determined direction, and upon reaching ON state of aforementioned detection signal the output signal from R5 is reset to terminate the functions of the motor and clutch.

While the terminals R0-R2 and R9 release successive clock signals in case of key entry, namely prior to the start of copying, the output signals for controlling the various loads after the start of copying cycle are of a length required to switch off said loads.

If the transfer paper input signal CPIS is not detected upon release of set signal from R6, the terminal R10 releases a single pulse signal to give a Feed Missing Display. Also if the transfer paper is jammed and cannot be ejected (CPOS signal not detected upon R4 set signal), the terminal R10 releases two pulse signals to perform a Transfer Paper Jam Display. Furthermore if the sheet original is jammed so that the second detector OS2 is not actuated, the terminal R10 releases three pulses to perform a Sheet Original Jam Display. For this purpose there is provided a counter 272 of which output terminals 1, 2 and 3 release display drive signals, which are reset by a drum rotation stop signal R4 and a delayed signal after the power switch-on, namely by the start of drum rotation or by the power switch-on.

A condenser of 47 μF connected to the CPU constitutes a CPU reset circuit when the power is switched on.

Now the interior of the computer chip element will be explained in the following, while making reference to FIG. 28. ROM is a read-only memory storing the master program for performing the sequence of the copier in predetermined order in the addresses thereof, and allowing the contents thereof by designating the addresses thereof. In said ROM the programs (key entry program, equipment function program, machine ending program etc.) in binary codes are stored from an address 0 to a necessary final address.

RAM is a random access memory for storing the copy number and the control signal temporarily during the copying process.

KI is an input section for receiving external signals. ID is an instruction decoder for decoding the code signals from the ROM and dividing said code signals into finer control signals α for conducting each step.

ALU is an arithmetic logic unit for data processing, and Acc is an accumulator for storing the input and output data and the result of logic processing. R0 is register with a latch function, of which content is utilized as control output signals.

The CPU and the peripheral circuits explained above perform the key entry flow, process sequence flows in book and sheet modes, finishing mode flow etc. shown in FIGS. 16-20, according to the detailed flow chart by instruction codes shown in FIG. 31 and program code lists shown in Tabs. 1 and 2.

The ROM in CPU stores the above-mentioned lists in binary codes and in the order of steps, said codes being read at an extremely high speed (for example 10 μsec for each step in the flow shown in FIG. 31) to perform the above-mentioned flows.

For simplicity the power supplies to the CPU and the peripheral circuits and the clock pulse source for driving the CPU are omitted from the foregoing explanation.

(Key entry cycle)

FIG. 20 shows the interaction between the RAM and keys in the key entry flow.

Upon power on, all the outputs of microprocessor are cleared, and the content of RAM is cleared. Then a data "1" is stored in the location (0, 1) of the RAM (hereinafter called location 1) and the flow proceeds to the key entry cycle.

The key entry is performed by means of numeral keys 126, a Clear key 127 for copy number correction, a book mode copy start key 130, a sheet mode copy start key 131 and stop keys 129 for stop instructions.

The copy number can be selected with two digits up to 99, of which first order and second order are stored respectively in the RAM location 1 and location 2. If no key is depressed a number "01" is displayed due to the content RAM location 1 previously set as explained above, thus always allowing single copying without actuating the numeral keys. If two or more copies are needed, the numeral keys are depressed accordingly. Upon actuation of any key, an identification step is conducted to identify if said key is a numeral key or another key, and, if identified as a numeral key, the flow stores the input numeral into the RAM location 1 with corresponding display and awaits the next key actuation.

If it is identified as the clear key, the data in RAM locations 1 and 2 are cleared, and the flow stores again "1" in the RAM location 1 and awaits the next key actuation. The flow proceeds to the succeeding cassette change step upon depression of a copy start key. Then an identification is performed to identify if a stop signal is released, and, if yes, the program again awaits the next key actuation. If no, the program proceeds to the copy sequence.

The stop signal is released if the transfer sheet or the developer is lacking or when the fixing heater has not reached a predetermined temperature.

If numeral keys are actuated twice in succession, the data in the RAM location 1 is transferred to the location 2, and the second data is stored in the RAM location 1. For example in case of 72 copies, the data storage is conducted as shown in FIG. 29.

Upon succeeding actuation of any keys other than numeral keys the program performs the functions in same manners as explained before.

When the program has passed the key entry program and entered the copy sequence, the keys no longer provide input data even if depressed, thereby preventing erroneous functions.

(Process sequence)

FIGS. 16-18 show sequence control flow charts from power put-on to the end of copying in the copier according to the present invention, and FIGS. 19 and 20 are time charts indicating the function timings of process means.

The timing signals for performing the process after the power on and the copy instruction by the foregoing key entry cycle are formed based on the clock signals CP of 1 pulse per 1 mm of process speed (drum rotation speed 100 mm/sec).

After the main switch is turned on, the copy sequence is not initiated for a waiting time during which the fixing heater is energized and reaches a predetermined temperature.

After the lapse of said waiting time, the copy sequence is rendered possible if the transfer sheet and the toner are properly provided.

(Cassette change)

There are provided three cassettes, of which the upper and lower cassettes accommodate the standard sizes of higher frequency of use to enable copying of two sizes without manual cassette exchange. Also there is provided a manually inserted (auxiliary) cassette for enabling use of a transfer paper of a non-standard size.

These three cassettes can be selected by the button switches 122, 123 and 124.

As both the upper cassette and the auxiliary cassette utilize the same paper feed device, either cassette not in use is to be placed so as not to interfere with the paper feed from the other cassette. This state is detected by a microswitch 100 functioning in connection with the cassette displacing mechanism. Said mechanism is driven by a motor 108 which is controlled by said microswitch.

Namely upon selection of the auxiliary cassette, the presence thereof in the determined position is detected by the ON state of the switch 100 (ACS), but in case of OFF state thereof the cassette motor connected with a cam 101 is rotated to expel the upper cassette toward the outside and set the auxiliary cassette to the determined paper feed position until said switch becomes ON. On the other hand when the upper cassette is selected, the motor is rotated until the point b reaches the switch 100 to retract the auxiliary cassette and set the upper cassette instead.

In FIG. 2, 150 and 151 respectively indicate a lamp and a light-receiving element for detecting transfer paper in each cassette.

(Book mode)

Now the process sequence in the book mode copying will be explained with reference to the flow chart in FIG. 16 and the time chart in FIG. 21.

The copy sequence is initiated by depressing the copy button 130. At first a drum drive motor 112 is switched on to initiate the rotation of photosensitive drum, and simultaneously initiated is the counting of clock pulses CL as well as the preliminary charging and exposure to reduce the potential unevenness on the photosensitive drum, by means of the output signals from R4 and R9. Upon counting 300 pulses, the output signals from R0 and R7 turn on the primary charger 10, AC discharger 12, flush exposure lamp 13, liquid squeeze charger 16, transfer charger 17 and blank exposure lamp 102. Upon further counting of 120 clock pulses, the optical system displacing clutch 109 is turned on by the output signal from R5 to advance the optical system from the home position. Further a register clutch 110 is turned on by the output signal of R2 to cause the rotation of register roller 52. Upon further counting of 6 clock pulses a paper feed plunger 113 is energized by the output signal of R1 to lower the constantly driven paper feed roller 53 to advance the transfer paper from the cassette 73, 74 or 75. Also the original illuminating lamp 3 is lighted by the output signal of R6 and starts displacement with the optical system 4, 5 while illuminating the surface of an original. Also the blank exposure lamp 102 is turned off.

Upon counting of 60 pulses after the paper feed, the detector 103 performs the detection of paper 20, and, if not detected, the program proceeds to the routine F whereby the terminal R10 releases a single pulse to give a feed missing display.

In such case all the drive systems are turned off except the heater control and the feed drive motor 111 which are maintained in function. In case the upper 74 or the lower cassette 73 is utilized, the program proceeds to the routine G, and the copying sequence is restarted by depressing the start button after removing the transfer paper incorrectly fed. In case of the auxiliary cassette 75, the feed missing display indicates the absence of paper therein as this cassette is not provided with means for detecting the remaining amount of paper therein. In this case the cassette motor 108 is started to expel the auxiliary cassette to the outside to a determined position at which the microswitch 100 is turned off to terminate the function of the cassette motor 108. By again depressing the start button after inserting the transfer sheets into the cassette, the cassette motor is activated to guide the cassette into the machine, and upon reaching a determined position the microswitch 100 is actuated as shown in FIG. 26(D) to release a signal, which terminates the function of the cassette motor and starts the copy sequence.

If the transfer sheet arrives within afore-mentioned counting of 50 clock pulses, and upon further counting of 50 clock pulses from said arrival, the register clutch 110 is disconnected to stop the rotation of the register rollers 52 whereby the leading end of the transfer paper collides with said rollers to temporarily stop the advancement thereof. Thereafter a register signal RS released by a switch 116 upon passing of the optical system through a determined position connects the register clutch to start the rotation of said register rollers, thereby causing the advancement of transfer paper through said rollers toward the drum. Said register signal is released at a timing in such a manner that the leading end of the image formed on the drum coincides with the leading end of said transfer paper.

Upon receipt of the register signal, the paper feed plunger 103 is deactivated to terminate the paper feed function of the paper feed roller.

Upon passing of the transfer paper through the detector 113, the exposure lamp 3 and the optical system displacing clutch 109 are both turned off, whereby the optical system is made free and returned to the home position by means of the spring. During said reversing displacement of the optical system, there is lighted the blank exposure lamp 102. Also the preset copy number is reduced by one. If after a jam reset operation which is to be explained later, this subtraction does not take place in order to compensate the loss of jammed copy.

The program checks the remaining copy number, and, if 0, proceeds to the finishing mode (routine D). If it is not 0, the copying sequence further proceeds. Also the program proceeds to the finishing mode if there is released, at this point, a copy stop signal (by depression of the stop button or by the lack of transfer paper or toner).

In the absence of said stop signal, upon receipt of the register signal RS released at the reversing of the optical system, there is conducted a counting of 124 clock pulses, of which period is selected slightly longer than the time from the signal release of register signal generator to the return of optical system to the home position. Upon completion of counting of 124 pulses, the optical system is ready to start from the home position for starting the succeeding copying cycle.

As the developing device is functioned in synchronization with the main motor, the photosensitive drum is rotated upon counting 300 clock pulses after the end of copying whereby the surface thereof is cleaned with the developer and the blade 25.

(Sheet mode)

In the following there will be explained the sequence control in sheet mode while making reference to the time charts in FIGS. 22 and 23 and to the flow chart in FIG. 17.

The optical system to be used is same as that used in the book mode. Thus the optical system, if placed in a position for the book mode, is displaced to the position determined for the sheet mode by depressing the sheet start button 131. The optical system advanced by the displacing motor therefore the forward clutch is stopped upon actuating a microswitch 104 (OHP2), and simultaneously the exposure lamp 3 is deflected to a direction shown in FIG. 1 adapted for the sheet copying.

Successively, in a similar manner as in the book mode, there is conducted the selection of a cassette followed by the turning on of the drum motor, preliminary exposure lamp, preliminary charger, primary charger, AC discharger, transfer charger, whole surface (flush) exposure lamp and blank exposure lamp, and thereafter the sheet mode sequence (routine C) is started upon counting of 120 clock pulses.

Upon completion of counting of said 120 pulses, the sheet clutch is energized to start the rotation of feed roller 29, by which the stacked sheet originals are conveyed, sheet by sheet, from the tray 27. At the same time the register clutch is also connected. Upon counting of 100 clock pulses after the leading end of an original by the first original detector 106 (OS1 on), the paper feed plunger 113 is energized to supply the transfer paper from the cassette and to light the original exposure lamp 3, while extinguishing the blank exposure lamp 102. In this manner the image exposure is conducted while the original is transferred, thereby performing the latent image forming process. Also upon counting of 50 clock pulses after the start of paper feeding there is identified if the transfer paper has reached the detector 103, thus to judge the presence of error in paper feeding in a same manner as explained before. Upon identification of correct arrival of the transfer paper there is further identified if the leading end of an original reaches the second detector 107 within further 60 clock pulse counting. In case of absence of the arrival of the original (OS2 off), the program, judging that the original is jammed on the way, interrupts the copying sequence and releases three pulses from the terminal R10 to perform the original jam display.

The copy cycle of sheet mode can be restarted by depressing the sheet start button again after the jammed original is eliminated.

If the second detector 107 detects the original within said 60 clock pulses, there is further conducted a counting of 50 clock pulses from said detection, upon completion of which the register clutch is disconnected to stop the rotation of register rollers 52, whereby the advancement of the transfer paper is interrupted. Upon further counting of 50 clock pulses the register clutch is connected to start the advancement of the transfer paper thereby keeping the leading ends of said paper and of developed image on the drum in register. The paper feed plunger is deactivated as the transfer paper is pinched between the register rollers.

The counter for counting the original number is increased by one when an original has passed through the first detector 106.

This result is stored in the above-mentioned location of the RAM (FIG. 29) and is displayed in succession from 01 on the above-mentioned copy number display device 125. It is to be noted that the copy number setting and the corresponding display by the numeral keys are forbidden in the sheet mode operation.

Thereafter the program checks if the copying cycle is to be continued or to be temporarily interrupted (due to the absence of transfer paper or toner, or by the actuation of stop button). If the stop instruction is given, the program extinguishes the exposure lamp 3 and turns on the blank exposure lamp when the transfer paper has passed the detector 103 and proceeds to the finishing mode (FIG. 18).

Even in case the copying is to be continued, if a next original does not reach the first detector 106 within 50 clock pulses after the passing of the preceding original through the first detector, the program turns off the exposure lamp and turns on the blank exposure lamp upon completion of passing of the transfer paper and proceeds to the finishing mode.

If a next original arrives at the first detector 106 within the above-mentioned 50 clock pulses, there are further counted 50 clock pulses (i.e. 100 pulses in total) whereupon the program waits the passing of the transfer paper. If the transfer paper is still in transfer, the next original cannot be advanced as the next transfer paper cannot be fed. In such case, therefore, the sheet clutch is disconnected to temporarily stop the transfer of original (cf. time chart in FIG. 22). Upon completion of the passing of the transfer paper, the sheet clutch is immediately connected to restart the advancement of original, and simultaneously the paper feed plunger 113 is energized to feed the next transfer paper. Thereafter continued are the sequences of exposure, transfer and finishing in the above-mentioned manner.

On the other hand, in case of a short-sized transfer paper of which passing can be detected within 100 clock pulses after passing the first detector, the program follows the time chart shown in FIG. 23. In this case the sheet clutch is not disconnected but maintained in function to continue the original feeding and exposure, and the transfer paper is fed at the 100th pulse.

The sequence control thereafter is conducted in the above-mentioned manner.

As explained in the foregoing, the control of start of original exposure by detecting the trailing end of the transfer paper renders possible a high-speed continuous copying regardless of the size of the original and of the transfer paper.

The detection signals from the detectors 106, 107 and 103 are respectively called S1, S2 and S3.

Another example of sheet mode control according to the size as mentioned above can be realized by the circuit shown in FIG. 24, wherein COPY is a copy button, DISC is a high voltage source, M is a drum motor, Blank is a blank exposure lamp, S.CL is a sheet clutch, R.CL is a register clutch, LAMP1 is an exposure lamp, PL is a paper feed plunger, CUP is determined copy number completion signal, S1' is the second or thereafter of the signal S1, COUT is a counter for counting the signal S1, CUT1-5 are counters for counting clock pulses CL and adapted for generating a pulse upon counting clock pulses of a determined number, wherein CUT5 releasing a step signal upon counting clock pulses of a determined number and being reset by the input of said signal to the terminal R; S1 and S3 are inverted signals of the signals S1 and S3, G1-G3 are AND gates and G9-G12 are OR gates; and the operation elements (motor etc.) are on-off controlled by the output signals (M etc.) released in the above-mentioned circuit.

The function of said circuit follows the aforementioned timing chart and will not be explained in detail.

Now there will be given an explanation on the function of the CPU in, as an example, the control for optical system displacement as a preparation for scanning directly prior to performing the sheet mode sequence, while making reference to a part of the above-mentioned detailed flow chart.

In the sheet mode operation the optical system, as explained before, has to be located in a position exclusively designed for this mode. If not located in such position, the optical system is displaced by the rotation of the displacing motor therefor and the actuation of the forward clutch, the position detection switch 104 is actuated upon arrival of the optical system at the stop position. Upon detection of actuation of said switch, the displacing motor and the forward clutch are immediately disconnected whereby the optical system stops at a position exclusive for the sheet mode.

The above-mentioned sequence will be further explained with reference to the program steps shown in FIG. 30(A) and (B).

The ROM releases a control signal (code) for each step by the clock pulses for driving the CPU. The output signals thus obtained are decoded by the instruction decoder ID to perform the program in succession. At first, upon output of a control code from a RAM location corresponding to the step 1, the decoder ID decodes this control code, and a numeral 9 is stored in the register YR through ALU by the control signal 2₁ to ALU and YR. In the step 2 a register R9, designated by said register YR among the registers RO, is set. In the step 3 the input data in the key input section KI is stored through ALU into the accumulator Acc. As the output of register R9 is released at the step 1, the input of the optical system home position detecting switch OHP2 is selected and it is identified if said switch OHP2 is open or closed (cf. matrix circuit in FIG. 26). Thus an input signal "0" or "1" of K4 in the key input section KI is stored in the accumulator Acc as a code of which second bit corresponds to the K4. Then in the step 4 a numeral "0" is set in the register YR through ALU.

In the step 5 the data stored in the accumulator Acc in the step 3 is transferred and stored in the location (O, O) of the memory RAM designated by the register YR. In the step 6 it is identified if the second bit of the data in said memory location (O, O) is "1" or not. If the data is "1" (yes) signifying that the optical system is identified to be in the position for sheet mode, the next step 7 is conducted. On the other hand if the data is "0" (no) signifying the failure of identification, the step 7 is skipped and the next step 8 for displacing the optical system is conducted. In the step 8 a numeral "5" is set in the register YR. In the step 9 the register R5 which is designated by said register YR among the registers RO, is set, and the output thereof is supplied to the driver to switch on the forward clutch. Thus, in combination with the above-mentioned output of the register R9, the optical system starts to displace toward the position for sheet mode (cf. FIG. 26). The step 10 is a jump instruction with a label LB1 to return to the step 1, and this loop function is repeated until the detecting switch OHP2 becomes actuated. When the OHP2 is actuated upon arrival of the optical system at the position for sheet mode, the second bit of the input data becomes "1" whereupon conducted is the step 7 which is a jump instruction to a label LB2. Thus successively performed is the step 11 designated by LB2. The step 11 stores a numeral "9" in the register YR, and the next step 12 resets the register R9 which is selected, among the registers RO, by said register YR. Similarly the register R5 is reset in the steps 14 and 15. In this manner the outputs of registers R9 and R5 are reset to switch off the displacing motor and the forward clutch, whereby the optical system is stopped at the position for sheet mode.

The register addresses of the RAM are schematically shown in FIG. 29.

The location (O, O) corresponds to the position of memory in the step 5 in FIG. 30 explained above. This location is utilized as a test bit for identifying the input signals. The addresses 5 and 6 are utilized as registers for storing "1" by the flag instructions and used as routine identifying means in other flow steps in FIG. 31. Also in FIG. 29 there are shown registers for storing the input copy number in the key entry cycle (addresses 3 and 4), for storing the finished copy number in the sequence flow cycle (addresses 1 and 2), for storing clock pulse number to be counted for jam identification (addresses 9-11) and for storing clock pulse numbers to be counted for load control timing (addresses 7 and 8).

In the present invention the preset copy number on the counter is subtracted by one at each copy completion but the copying of same number can be repeated by simply depressing the start button since the preset copy number is still memorized in the memory addresses 3 and 4.

The stop flag, entry flag etc. are stored in a same bit area because they have different timings, thus economizing the registers.

The flags employed in FIGS. 29 and 31 are as follows:

display flag: set for driving display unit D1

stop flag: set when temporary stop, no paper etc.

entry flag 1: set after key entry

entry flag 2: set after entry "1"

jam flag 1: set when paper is jammed

jam flag 2: set when pulse count for jam identification reaches a preset number

clear flag: set when clear key is actuated

sheet mode flag: set when sheet mode is selected

auxiliary cassette flag: set when auxiliary cassette is selected

pulse flag 1: set when the pulse count does not reach a preset number

pulse flag 2: set when the pulse number for jam identification is preset

The functions of CPU in the key entry, sequence control and finishing flow are detailedly shown also in the flow charts of FIG. 31.

(Jam detection)

If the transfer paper reaches the outlet within a determined period after the feeding thereof from the register rollers 52 is checked by identification of paper arrival at the outlet after counting a determined number of clock pulses CP released in response to the drum rotation. The paper arrival is detected by the microswitch 117 which thereupon releases the transfer paper discharge signal CPOS. The counting of clock pulses is started from the timing of release of transfer paper from the register rollers 52. The CPU, performing very fast functions, is capable of achieving various controls between two clock pulses. Thus the clock pulse counting for jam detection can be performed without affecting the controls on various elements by incorporating a clock counting program for jam detection into the main flow while awaiting various input signals or counting clock pulses for control timing. Stated otherwise different pulse countings can be conducted at the same time.

More specifically there is provided a flow (FIG. 19 I₁ -I₂) for setting "300" in the RAM locations 9-11 after the second turning on of the register clutch shown in FIG. 16, and also there is provided a jam detection flow I₂ -I₃ for identifying the 300 pulses within the timing identification loop for load function, for example the CP1 count step or register signal identification loop step.

If the paper does not reach the detector 117 upon jam detection check, all the drives (particularly those of higher danger such as high-voltage source, heater etc.) are cut off to interrupt the copying operation, and the transfer paper jam display lamp is lighted. The paper conveyor belt is maintained in function to allow paper ejection. The optical system may be an obstacle in removing the paper jammed in the machine. For this reason upon detection of paper jamming the output terminals R9 and R5 are set to drive the optical system displacing motor 114 thereby displacing the optical system to the position for sheet mode. Upon reaching the determined position the optical system actuates the microswitch 104 to release the signal OHP2 thereby turning off the signal R5 to cut off said displacing motor. In this case the optical system is mechanically locked and is therefore not reversed. The output signal from R9 is still maintained.

Opening and reclosing of the upper cover for jammed paper removal actuates a microswitch 105 (FIG. 3), to release a signal for resetting the jam detection, the input of said signal being performed by the output R9 shown in FIG. 26(A).

Upon repressing thereafter of the start button the output R9 is terminated to actuate a plunger 115 for releasing the optical system which thus is released from the locking and is reversed to the home position for book mode by means of a spring.

It is also possible to displace the charger 17 and roller 21 upon jam detection in order to facilitate jammed paper elimination.

The above-mentioned clock pulses are generated, by means of an internal generator, at a rate of 1 pulse/mm of process speed.

Said clock pulses can be generated, for example, by optically detecting the holes provided on a rotor plate rotating with the rotation speed of the drum.

Although the conventional discrete control circuit has to be provided with a key entry prohibition circuit to prohibit key entries during the copying operation, the control system of the present invention is free from erroneous operation even when, for example, the start button for sheet mode is depressed during the copying operation in book mode since the sequential control by microprogramming does not accept the key entries once the copy cycle is started after the proper key entries. Such technology utilizing stored program is also applicable to the copiers of various copying modes such as A4/A3 sizes, one-side and two-side copying, reduced size and same size copying.

As to the terms used in FIG. 31 and Tab. 1, reference should be made to the TMS 1000 Series, "Programmer's Reference Manual" published by Texas Instruments.

                  TABLE 1                                                          ______________________________________                                         Program Step                                                                   GENERAL ASSEMBLER                                                              ASSEMBLE OF TMS1000 NEW INSTRUCTION FOR B.B                                    STMT      SOURCE     STATEMENT                                                 ______________________________________                                          1        OPT        LIST,XREF, PROM, STAT                                      2        TNI06      SEQUENCE PROGRAMME                                         3        PAGE       0                                                          4 LB9    ALEC       1                                                          5        BR         LB314                                                      6        ALEC       2                                                          7        BR         LB14                                                       8        ALEC       4                                                          9        BR         LB15                                                       10       TCMIY      3                                                          11       BR         LB16                                                       12 LB314 BL         LB315                                                      13 LB13  TCMIY      0                                                          14       BR         LB16                                                       15 LB14  TCMIY      1                                                          16       BR         LB16                                                       17 LB15  TCMIY      2                                                          18       BR         LB16                                                       19 LB10  TCY        0                                                          20       ALEC       1                                                          21       BR         LB17                                                       22       ALEC       2                                                          23       BR         LB18                                                       24       ALEC       4                                                          25       BR         LB19                                                       26       TCMIY      7                                                          27       BR         LB16                                                       28 LB17  TCMIY      4                                                          29       BR         LB16                                                       30 LB18  TCMIY      5                                                          31       BR         LB16                                                       32 LB19  TCMIY      6                                                          33       BR         LB16                                                       34 LB11  TCY        0                                                          35       ALEC       1                                                          36       BR         LB20                                                       37       TCMIY      9                                                          38       BR         LB16                                                       39 LB20  TCMIY      8                                                          40       BR         LB16                                                       41 LB12  ALEC       1                                                          42       BR         LB21                                                       43       ALEC       2                                                          44       BR         LB22                                                       45       TCY        0                                                          46       TCMIY      0                                                          47       TCMIY      0                                                          48       TCY        5                                                          49       SBIT       3                                                          50       BR         LB16                                                       51 LB22  TCY        6                                                          52       SBIT       0                                                          53 LB21  TCY        7                                                          54       SETR                                                                  55       KNEZ                                                                  56       BR         LB23                                                       57       RSTR                                                                  58       BL         LBSQ                                                       59 LB23  RSTR                                                                  60       BL         LB24                                                       61 LB16  TCY        5                                                          62       LDP        1                                                          63       BR         0                                                          64       PAGE       1                                                          65       TBITI      1                                                          66       BR         LB25                                                       67       TBITI      2                                                          68       BR         LB26                                                       69 LB27  TCY        1                                                          70       TMA                                                                   71       IYC                                                                   72       TAM                                                                   73       TCY        4                                                          74       TAM                                                                   75       TCY        0                                                          76       TMA                                                                   77       IYC                                                                   78       TAM                                                                   79       TCY        3                                                          80       TAM                                                                   81       TCY        5                                                          82       SRIT       1                                                          83 LB24  CALL       SUBA                                                       84       CALL       SUBB                                                       85       CALL       SUBA                                                       86       CALL       SUBB                                                       87       TCY        5                                                          88       TBITI      3                                                          89       BR         LB28                                                       90 LB25  TBITI      3                                                          91       BR         LB309                                                      92       BL         LB4                                                        93 LB309 BL         LB3                                                        94 LB28  BL         LB3                                                        95 LB26  RBIT       2                                                          96       TCY        1                                                          97       TCMIY      0                                                          98       BR         LB27                                                       99 LBSQ  CALL       SUBA                                                      100       TCY        6                                                         101       TBITI      0                                                         102       BR         LB36                                                      103       LDP        2                                                         104       BR         0                                                         105 LB36  BL         LBSMI                                                     106       PAGE       2                                                         107 LB37  CALL       SUBA                                                      108       TCY        3                                                         109       CALL       SUBC                                                      110       TBITI      3                                                         111       BR         LB30                                                      112 LB31  TCY        3                                                         113       CALL       SUBE                                                      114       TBITI      1                                                         115       BR         LB32                                                      116       TBITI      2                                                         117       BR         LB33                                                      118       TBITI      0                                                         119       BR         LB33                                                      120       TCY        3                                                         121       RSTR                                                                 122       BR         LB37                                                      123 LB32  CALL       SUBA                                                      124       BR         LB31                                                      125 LB30  TCY        6                                                         126       SBIT       1                                                         127 LB34  TCY        3                                                         128       CALL       SUBE                                                      129       TBITI      1                                                         130       BR         LB33                                                      131       CALL       SUBA                                                      132       BR         LB34                                                      133 LB33  TCY        3                                                         134       RSTR                                                                 135       TCY        4                                                         136       SETR                                                                 137       TCY        7                                                         138       TCMIY      6F                                                        139       TCMIY      6F                                                        140 LB38  CALL       SUBD                                                      141       TCY        6                                                         142       TBITI      3                                                         143       BR         LB39                                                      144       TCY        7                                                         145       TCMIY      6D                                                        146       TCMIY      64                                                        147 LB40  CALL       SUBD                                                      148       TCY        6                                                         149       TBITI      3                                                         150       BR         LB41                                                      151       TCY        0                                                         152       SETR                                                                 153       TCY        7                                                         154       SETR                                                                 155       LDP        3                                                         156       BR         0                                                         157 LB39  CALL       SUBA                                                      158       BR         LB38                                                      159 LB41  CALL       SUBA                                                      160       BR         LB40                                                      161       PAGE       3                                                         162       TCMIY      6E                                                        163       TCMIY      6E                                                        164 LB42  CALL       SUBD                                                      165       TCY        6                                                         166       TBITI      3                                                         167       BR         LB43                                                      168       TBITI      0                                                         169       BR         LB44                                                      170 LB311 TCY                                                                            5                                                                    171       SETR                                                                 172       TCY        2                                                         173       SETR                                                                 174       TCY        7                                                         175       SETR                                                                 176       TCMIY      5                                                         177       TCMIY      0                                                         178 LB45  CALL       SUBD                                                      179       TBITI      2                                                         180       BR         LB326                                                     181 LB325 TCY        6                                                         182       BR         LB327                                                     183 LB326 TCY        0                                                         184       TBITI      2                                                         185       BR         LB325                                                     186       BL         LBJAMN 82                                                 187 LB327 TBITI      3                                                         188       BR         LB46                                                      189       SETR                                                                 190       TCY        1                                                         191       SETR                                                                 192       TCY        7                                                         193       RSTR                                                                 194       TCMIY      6D                                                        195       TCMIY      6C                                                        196 LB47  CALL       SUBD                                                      197       TBITI      2                                                         198       BR         LB329                                                     199 LB328 TCY        6                                                         200       BR         LB330                                                     201 LB329 TCY        0                                                         202       TBITI      2                                                         203       BR         LB328                                                     204       BL         LBJAMN82                                                  205 LB330 TBITI      3                                                         206       BR         LB48                                                      207       TCY        0                                                         208       LDP        4                                                         209       BR         0                                                         210 LB43  CALL       SUBA                                                      211       BR         LB42                                                      212 LB46  CALL       SUBA                                                      213       BR         LB45                                                      214 LB48  CALL       SUBA                                                      215       BR         LB47                                                      216 LB44  BL         LBSM2                                                     217       PAGE       4                                                         218       TBITI      3B                                                        219       BR         LBBO                                                      220                                                                            221 LB107 TCY        9                                                         222 LB50  RSTR                                                                 223       DYN                                                                  224       BR         LB50                                                      225       TCY        10                                                        225       SETR                                                                 226       RSTR                                                                 227       TCY        6                                                         228       TBITI      1                                                         229       BR         LB53                                                      230       BR         LB54                                                      231 LB53  TCY        3                                                         232       CALL       SUBE                                                      233       TBITI      1                                                         234       BR         LB55                                                      235       TCY        3                                                         236       RSTR                                                                 237 LB54  BL         LB87                                                      238 LB55  CALL       SUBA                                                      239       BR         LB53                                                      240 LB49  TCY        7                                                         241       TCMIY                                                                242       TCMIY      6C                                                        243 LB57  CALL       SUBD                                                      244       TBITI      2                                                         245       BR         LB332                                                     246 LB331 TCY        6                                                         247       BR         LB333                                                     248 LB332 TCY        0                                                         249       TBITI      2                                                         250       BR         LB331                                                     251       BL         LBJAMN82                                                  252 LB333 TBITI      3                                                         253       BR         LB58                                                      254       TCY        2                                                         255       RSTR                                                                 256 LB60  CALL       SUBF                                                      257       TBITI      1                                                         258       BR         LB61                                                      259       CALL       SUBA                                                      260       BR         LB60                                                      261 LB61  TCY        1                                                         262       RSTR                                                                 263       TCY        2                                                         264       SETR                                                                 265       TCY        6                                                         266       SBIT       2                                                         267       TCY        9                                                         268       TCMIY      6D                                                        269       TCMIY      64                                                        270       LDP        5                                                         271       BR         0                                                         272 LB58  CALL       SUBA                                                      273       BR         LB57                                                      274       PAGE       5                                                         275       TCMIY      68                                                        276 LB65  CALL       SUBD                                                      277       TCY        0                                                         278       TBITI      3                                                         279       BR         LB310                                                     280       BR         LB334                                                     281 LB310 TCY        5                                                         282       TBITI      2                                                         283       BR         LB335                                                     284 LB67  CALL       SUBA                                                      285       BR         LB65                                                      286 LB335 TCY        0                                                         287       TBITI      2                                                         288       BR         LB67                                                      289       BL         LBJAM                                                     290 LB334 TCY        5                                                         291       RSTR                                                                 292       TCY        6                                                         293       RSTR                                                                 294       TCY        7                                                         295       SETR                                                                 296       TCY        5                                                         297       TBITI      3                                                         298       BR         LD300                                                     299       TCY        1                                                         300       DMAN                                                                 301       BR         LB71                                                      302       A10AAC                                                               303       TAM                                                                  304       TCY        2                                                         305       DMAN                                                                 306 LB71  TAM                                                                  307       BR         LB70                                                      308 LB300 RBIT       3                                                         309 LB70  TCY        1                                                         310       MNEZ                                                                 311       BR         LB301                                                     312       TCY        2                                                         313       MNEZ                                                                 314       BR         LB301                                                     315 LB69  TCY        7                                                         316       TCMIY      6E                                                        317       TCMIY      63                                                        318 LB73  CALL       SUBD                                                      319       TBITI      2                                                         320       BR         LB339                                                     321 LB340 TCY        6                                                         322       BR         LB341                                                     323 LB339 TCY        0                                                         324       TBITI      2                                                         325       BR         LB340                                                     326       BL         LBJAMN                                                    327 LB341 BL         LB343                                                     328 LB301 BL         LB336                                                     329       PAGE       6                                                         330 LB343 TBITI      3                                                         331       BR         LB74                                                      332       TCY        0                                                         333       RSTR                                                                 334       TCY        2                                                         335       RSTR                                                                 336       TCY        7                                                         337       RSTR                                                                 338       TCY        8                                                         339       RETR                                                                 340       TCY        7                                                         341       TCMIY      63                                                        342       TCMIY      64                                                        343 LB76  CALL       SUBD                                                      344       TBITI      2                                                         345       BR         LB345                                                     346 LB344 TCY        6                                                         347       BR         LB346                                                     348 LB345 TCY        0                                                         349       TBITI      2                                                         350       BR         LB334                                                     351       BR         LBJAMN                                                    352 LB346 TBITI      3                                                         353       BR         LB77                                                      354       BL         LB81                                                      355 LBJAMN                                                                               TCY        5                                                         356       SBIT       3                                                         357 LBJAM CALL       SUBA                                                      358       TCY        9                                                         359 LB78  RSTR                                                                 360       DYN                                                                  361       BR         LB78                                                      362       TCY        10                                                        363       SETR                                                                 364       RSTR                                                                 365       SETR                                                                 366       RSTR                                                                 367       SETR                                                                 368       TCY        5                                                         369       SETR                                                                 370 LB79  TCY        9                                                         371       CALL       SUBE                                                      372       TBITI      2                                                         373       BR         LB80                                                      374       CALL       SUBA                                                      375       BR         LB79                                                      376 LB74  CALL       SUBA                                                      377       BL         LB73                                                      378 LB77  CALL       SUBA                                                      379       BR         LB76                                                      380 LB80  TCY        5                                                         381       RSTR                                                                 382       LDP        7                                                         383       BR         0                                                         384       PAGE       7                                                         385       TCY        9                                                         386       RSTR                                                                 387 LB82  CALL       SUBF                                                      388       TBITI      2                                                         389       BR         LB83                                                      390       CALL       SUBA                                                      391       BR         LB82                                                      392 LB83  CALL       SUBB                                                      393 LB84  CALL       SUBF                                                      394       TBITI      2                                                         395       BR         LB85                                                      396       CALL       SUBB                                                      402 LB85  CALL       SUBA                                                      403       BR         LB84                                                      404 LB87  TCY        9                                                         405       CALL       SUBC                                                      406       TBITI      0                                                         407       BR         LB88                                                      408       TBITI      1                                                         409       BR         LB89                                                      410 LB90  CALL       SUBA                                                      411       BR         LB87                                                      412 LB89  TCY        6                                                         413       TBITI      0                                                         414       BR         LB93                                                      415       BR         LB90                                                      416 LB88  TCY        6                                                         417       TBITI      0                                                         418       BR         LB92                                                      419 LB93  TCY        7                                                         420       CALL       SUBC                                                      421       TBITI      3                                                         422       BR         LB94                                                      423       TCY        10                                                        424       RSTR                                                                 425       TCY        5                                                         426       RBIT       1                                                         427       TCY        6                                                         428       RBIT       2                                                         429       BL         LB37                                                      430 LB92  CALL       SUBA                                                      431       BR         LB87                                                      432 LB94  CALL       SUBA                                                      433       BR         LB93                                                      434       PAGE       8                                                         435 LB81  TCY        7                                                         436       TCMIY      6F                                                        437       TCMIY      6F                                                        438 LB95  CALL       SUBD                                                      439       TCY        6                                                         440       TBITI      3                                                         441       BR         LB96                                                      442       TCY        4                                                         443       RSTR                                                                 444       TCY        5                                                         445       TBITI      1                                                         446       BR         LB56                                                      447       TCY        4                                                         448       TMA                                                                  449       TCY        2                                                         450       TAM                                                                  451       TCY        3                                                         452       TMA                                                                  453       TCY        1                                                         454       TAM                                                                  455 LB56  CALL       SUBA                                                      456       TCY        5                                                         457       TCFIIY     0                                                         458       TCMIY      0                                                         459       BL         LB4                                                       460 LB96  CALL       SUBA                                                      461       BR         LB95                                                      462 LBSM1 TCY        1                                                         463       TCMIY      0                                                         464       TCMIY      0                                                         465 LB97  TCY        9                                                         466       CALL       SUBE                                                      467       TBITI      2                                                         468       BR         LB98                                                      469       TCY        5                                                         470       SETR                                                                 471       CALL       SUBA                                                      472       BR         LB97                                                      473 LB98  TCY        9                                                         474       RSTR                                                                 475       TCY        5                                                         476       RSTR                                                                 477       TCY        5                                                         478       RSTR                                                                 479       BL         LB37                                                      480 LBSM2 TCY        2                                                         481       SETR                                                                 482       BL         LB99                                                      483       PAGE       9                                                         484 LB99  TCY        8                                                         485       CALL       SUBE                                                      486       TBITI      1                                                         487       BR         LB100                                                     488       CALL       SUBA                                                      489       BR         LB99                                                      490 LB100 TCY        7                                                         491       TCMIY      3                                                         492       TCMIY      6                                                         493 LB101 CALL       SUBD                                                      494       TCY        6                                                         495       TBITI      3                                                         496       BR         LB102                                                     497       TCY        1                                                         498       SETR                                                                 499       TCY        6                                                         500       SETR                                                                 501       TCY        7                                                         502       RSTR                                                                 503 LB103 TCY        7                                                         504       TCMIY      1                                                         505       TCMIY      3                                                         506 LB104 CALL       SUBD                                                      507       TCY        6                                                         508       TBITI      3                                                         509       BR         LB105                                                     510       TCY        0                                                         511       TBITI      3                                                         512       BR         LB106                                                     513       BL         LB107                                                     514 LB102 CALL       SUBA                                                      515       BR         LB101                                                     516 LB105 CALL       SUBA                                                      517       BR         LB104                                                     518 LB106 TCY        7                                                         519       TCMIY      11                                                        520       TCMIY      3                                                         521 LB108 CALL       SUBD                                                      522       TCY        6                                                         523       TBITI      3                                                         524       BR         LB312                                                     525       BL         LB0JAM                                                    526 LB312 TCY        0                                                         527       TBITI      1                                                         528       BR         LB109                                                     529       CALL       SUBA                                                      530       BR         LB108                                                     531 LB109 TCY        7                                                         532       TCMIY      3                                                         533       TCMIY      3                                                         534       LDP        10                                                        535       BR         0                                                         536       PAGE       10                                                        537 LB1144                                                                               CALL       SUBD                                                      538       TCY        6                                                         539       TBITI      3                                                         540       BR         LB115                                                     541       TCY        2                                                         542       RSTR                                                                 543       TCY        7                                                         544       TCMIY      3                                                         545       TCMIY      3                                                         546 LB116 CALL       SUBD                                                      547       TCY        6                                                         548       TBITI      3                                                         549       BR5        LB117                                                     550       TCY        1                                                         551       RSTR                                                                 552       TCY        2                                                         553       SETR                                                                 554 LB118 CALL       SUBF                                                      555       TBIT15     1                                                         556       BR5        LB119                                                     557       TCY        1                                                         558       IMAC                                                                 559       TAM                                                                  560       A6AAC                                                                561       BR         LB120                                                     562 LB122 TCY        6                                                         563       RSTR                                                                 564       TCY        7                                                         565       CALL       SUBC                                                      566       LDP        11                                                        567       BR         0                                                         568 LB115 CALL       SUBA                                                      569       BR         LB114                                                     570 LB117 CALL       SUBA                                                      571       BR         LB116                                                     572 LB119 CALL       SUBA                                                      573       BR         LB118                                                     574 LB120 TAM                                                                  575       TCY        2                                                         576       IMAC                                                                 577       TAM                                                                  578       A6AAC                                                                579       BR         LB121                                                     580       BR         LB120                                                     581 LB121 TAM                                                                  582       BR         LB122                                                     583       PAGE       11                                                        584       TBITI      3                                                         585       BR         LB123                                                     586       TCY        6                                                         587       SETR                                                                 588       TCY        7                                                         589       TCMIY      3                                                         590       TCMIY      3                                                         591 LB124 CALL       SUBD                                                      592       TCY        6                                                         593       TBITI      3                                                         594       BR         LB125                                                     595 LB129 CALL       SUBF                                                      596       TBITI      3                                                         597       BR         LB313                                                     598       BR         LB130                                                     599 LB313 CALL       SUBA                                                      600       BR         LB129                                                     601 LB130 TCY        6                                                         602       RSTR                                                                 603       TCY        7                                                         604       SETR                                                                 605       BL         LB69                                                      606 LB123 TCY        6                                                         607       SETR                                                                 608       TCY        5                                                         609       SBIT       1                                                         610       BR         LB129                                                     611 LB125 TCY        0                                                         612       TBITI      1                                                         613       BR5        LB131                                                     614       CALL       SUBA                                                      615       BR         LB124                                                     616 LB131 TCY        7                                                         617       TCMIY      3                                                         618       TCMIY      3                                                         619 LB132 CALL       SUBD                                                      620       TCY        6                                                         621       TBITI      3                                                         622       BR         LB133                                                     623 LB135 CALL       SUBF                                                      624       TBITI      3                                                         625       BR         LB136                                                     626       TCY        8                                                         627       SETR                                                                 628       TCY        1                                                         629       SETR                                                                 630       LDP        12                                                        631       BR         0                                                         632 LB133 CALL       SUBA                                                      633       BR         LB132                                                     634 LB136 TCY        8                                                         635       RSTR                                                                 636       CALL       SUBA                                                      637       BR         LB135                                                     638       PAGE       12                                                        639       TCY        6                                                         640       SBIT       2                                                         641       BL         LB103                                                     642 LB336 CALL       SUBF                                                      643       TBITI      3                                                         644       BR         LB302                                                     645 LB303 CALL       SUBD                                                      646       TBITI      2                                                         647       BR         LB337                                                     648       TCY        0                                                         649       BR         LB338                                                     650 LB302 TCY        5                                                         651       SBIT       1                                                         652       BL         LB69                                                      653 LB337 TCY        0                                                         654       TBITI      2                                                         655       BR         LB338                                                     656 LB350 BL         LBJAMN                                                    657 LB338 TBITI      1                                                         658       BR         LB304                                                     659       CALL       SUBA                                                      660       BR         LB303                                                     661 LB304 TCY        7                                                         662       TCMIY      3                                                         663       TCMIY      6E                                                        664 LB318 CALL       SUBD                                                      665       TBITI      2                                                         666       BR         LB347                                                     667 LB348 TCY        6                                                         668       TBITI      3                                                         669       BR         LB349                                                     670       BR         LB351                                                     671 LB349 CALL       SUBA                                                      672       BR         LB318                                                     673 LB347 TCY        0                                                         674       TBITI      2                                                         675       BR         LB348                                                     676       BR         LB350                                                     690       PAGE       13                                                        691 SUBB  TCY        15                                                        692       TCMIY      8                                                         693 LB202 DYN                                                                  694       BR         LB202                                                     695       DMAN                                                                 696       TAM                                                                  697       MNEZ                                                                 698       BR         LB202                                                     699       RETN                                                                 700 SUBD  SETR                                                                 701       TKA                                                                  702       RSTR                                                                 703       TCY        0                                                         704       TAM                                                                  705       RETN                                                                 706 SUBD  TKA                                                                  707       TCY        0                                                         708       TAM                                                                  709       TBITI      0                                                         710       BR         SUBD                                                      711 LB203 TKA                                                                  712       TCY        0                                                         713       TAM                                                                  714       TBITI      0                                                         715       BR         LB204                                                     716       BR         LB203                                                     717 LB204 TCY        7                                                         718       DMAN                                                                 719       BR         LB205                                                     720       TAM                                                                  721       TCY        8                                                         722       DMAN                                                                 723       BR         LB205                                                     724       TCY        6                                                         725       RBIT       3                                                         726       BR5        LB206                                                     727 LB205 TAM                                                                  728       TCY        6                                                         729       SBIT       3                                                         730 LB206 TBITI      2                                                         731       BR         LB322                                                     732       TCY        5                                                         733       RBIT       2                                                         734       BR         LB323                                                     735 LB322 TCY        9                                                         736       DMAN                                                                 737       BR         LB324                                                     738       TAM                                                                  739       TCY        10                                                        740       DMAN                                                                 741       BR         LB324                                                     742       TAM                                                                  743       TCY        11                                                        744       DMAN                                                                 745       BR         LB324                                                     746       TCY        6                                                         747       RBIT       2                                                         748       TCY        5                                                         749       SBIT       2                                                         750       BR         LB323                                                     751 LB324 TAM                                                                  752       TCY        5                                                         753 LB323 RETN                                                                 754       PAGE       14                                                        755 SUBA  TCY        5                                                         756       TBITI      0                                                         757       BR         LB200                                                     758       SBIT       0                                                         759       TCY        12                                                        760       RSTR                                                                 761       TCY        1                                                         762       TAM                                                                  763       TDO                                                                  764       TCY        11                                                        765       SETR                                                                 766       BR         LB201                                                     767 LB200 RBIT       0                                                         768       TCY        11                                                        769       RSTR                                                                 770       TCY        2                                                         771       TMA                                                                  772       TDO                                                                  773       TCY        12                                                        774       SETR                                                                 775 LB201 RETN                                                                 776 SUBE  SETR                                                                 777       TKA                                                                  778       TCY        0                                                         779       TAM                                                                  780       RETN                                                                 781 SUBF  TKA                                                                  782       TCY        0                                                         783       TAM                                                                  784       RETN                                                                 785 LB0JAM                                                                               TCY        10                                                        786 LB110 RSTR                                                                 787       DYN                                                                  788       BR         LB110                                                     789       TCY        10                                                        790       SETR                                                                 791       RSTR                                                                 792       SETR                                                                 793       RSTR                                                                 794       SETR                                                                 795       RSTR                                                                 796 LB111 TCY        9                                                         797       CALL       SUBC                                                      798       TBITI      1                                                         799       BR         LB112                                                     800       CALL       SUBA                                                      801       BR         LB111                                                     802 LB112 TCY        2                                                         803       SETR                                                                 804       BL         LB37                                                      805 LB315 TCY        5                                                         806       TBITI      2                                                         807       BR         LB316                                                     808       TCY        0                                                         809       BL         LB13                                                      810 LB316 BL         LB4                                                       811       PAGF       15                                                        812       LDP        15                                                        813       TCY        12                                                        814 LB1   RSTR                                                                 815       DYN                                                                  816       BR         LB1                                                       817       CLO                                                                  818       LDX        0                                                         819       CLA                                                                  820 LB2   TAM                                                                  821       DYN                                                                  822       BR         LB2                                                       823 LB3   TCY        1                                                         824       TCMIY      1                                                         825       TCY        3                                                         826       TCMIY      1                                                         827       TCY        5                                                         828       SBIT       2                                                         829 LB4   CALL       SUBA                                                      830       TCY        0                                                         831       SETR                                                                 832       TKA                                                                  833       RSTR                                                                 834       ALEC       0                                                         835       BR         LB305                                                     836       BL         LB9                                                       837 LB305 IYC                                                                  838       SETR                                                                 839       TKA                                                                  840       RSTR                                                                 841       ALEC       0                                                         842       BR         LB306                                                     843       BL         LB10                                                      844 LB306 IYC                                                                  845       SETR                                                                 846       TKA                                                                  847       RSTR                                                                 848       ALEC       0                                                         849       BR         LB307                                                     850       BL         LB11                                                      851 LB307 TCY        9                                                         852       SETR                                                                 853       TKA                                                                  854       RSTR                                                                 855       ALEC       0                                                         856       BR         LB308                                                     857       BL         LB12                                                      858 LB308 TCY        5                                                         859       RBIT       1                                                         860       RBIT       3                                                         861       CALL       SUBB                                                      862       CALL       SUBA                                                      863       CALL       SUBB                                                      864       BR         LB4                                                       865       END                                                                  ______________________________________                                     

What we claim is:
 1. An image forming apparatus, comprising:image forming means for forming an image; a plurality of keys including a start key for providing a start signal which instructs the start of image formation and a stop key for providing a stop signal which instructs the interruption of image formation, said plurality of keys being connected to a key matrix circuit which generates key input signals including the start signal and the stop signal; and control means, being connected to the key matrix circuit, for controlling image formation of said image forming means in accordance with a control program stored in a program memory having been selected on the basis of key input signals from the key matrix circuit, the control program including a key sensing program which senses the key input signals from the key matrix circuit; wherein, before the start of image formation, said control means senses key input signals including the start signal and the stop signal from the key matrix circuit, and controls said image forming means in response to the start signal so as to start image formation, and wherein, during image formation, said control means is responsive only to a stop signal from the key matrix circuit and controls said image forming means in response to the stop signal so as to interrupt immediately image formation.
 2. An image forming apparatus according to claim 1, further comprising preventing means for preventing the key input signals except the stop signal from being generated by the key matrix circuit, during image formation.
 3. An image forming apparatus according to claim 2, wherein said control means outputs scanning signals to the key matrix circuit and senses the key input signals in response to the output of the scanning signals, and said preventing means prevents the scanning signals from being provided to said plurality of keys except the stop key.
 4. An image forming apparatus according to claim 1, wherein said control means is a one-chip microcomputer which includes the program memory.
 5. An image forming apparatus according to claim 1, wherein said plurality of keys include numeral keys for providing condition signals which define the condition of image formation.
 6. An image forming apparatus according to claim 1, wherein said image forming means forms the image on a paper.
 7. An image forming apparatus, comprising:image forming means for forming an image; a plurality of keys including a start key for providing a start signal which instructs the start of image formation and a stop key for providing a stop signal which instructs the interruption of image formation, said plurality of keys being connected to a key matrix circuit which generates key input signals including the start signal and the stop signal; detection means for detecting an improper state of the apparatus, in the case image formation cannot be continued, and for generating an improper signal; and control means, being connected to the key matrix circuit, for controlling image formation of said image forming means in accordance with a control program stored in a program memory on the basis of key input signals from the key matrix circuit, the control program including a key sensing program which senses the key input signals from the key matrix circuit and process steps which acknowledge the improper signal output from said detection means; wherein, before the start of image formation, said control means senses key input signals from the key matrix circuit, and controls said image forming means in response to the start signal from the key matrix circuit so as to start image formation, and wherein, during image formation, said control means senses the stop signal from the key matrix circuit and the improper signal from said detection means, and controls said image forming means in response to the stop signal from the key matrix circuit or the improper signal from said detection means so as to interrupt immediately image formation.
 8. An image forming apparatus according to claim 7, further comprising preventing means for preventing the key input signals except the stop signal from being generated by the key matrix circuit during image formation.
 9. An image forming apparatus according to claim 8, wherein said control means outputs scanning signals to the key matrix circuit and senses the key input signals in response to the output of the scanning signals, and wherein said preventing means prevents the scanning signals from being provided to said key matrix circuit except for a stop key signal.
 10. An image forming apparatus according to claim 7, wherein said control means is a single chip microcomputer which includes a programmable memory.
 11. An image forming apparatus according to claim 7, wherein said plurality of keys includes numeral keys for providing condition signals which define the condition of image formation.
 12. An image forming apparatus according to claim 7, wherein said image forming means forms the image on a paper.
 13. An image forming apparatus according to claim 12, wherein said detection means detects a paper jam in the apparatus. 